Dual-task Walking Research Articles

Dual-Task Interference in Children with Down Syndrome and Chronological and Mental Age-Matched Healthy Controls.

Background. On the assumption that motor actions result from the interaction between cognitive, perceptual, and neurological mechanisms, neuromotor dysfunction–such as in children with Down Syndrome (DS)–is expected to affect the central coordination processes required for dual-task (DT) performance. There are few dual-task (DT) studies in individuals with DS, so the current study examined the effects of dual-tasking (DT) on walking performance in children with DS. Method. In this study, a motor-cognitive DT was used in 12 children with DS (10.5 ± 1.08 years, 6 female), 12 typically developed (TD) children with the same mental age (TD-MA: 5.98 ± 1.21 years, 6 female), and 12 with the same chronological age (TD-CA: 10.5 ± 1.07 years, 6 female). Children were asked to enumerate animals for one minute while walking straight ahead. Results. All groups showed lower performances under the DT condition than the single-task (ST) condition. Children with DS appear to have the most difficulties in motor and cognitive tasks and ST- and DT-conditions. Concerning the DT costs (DTC), difficulties were mainly observed with the motor task, with motor DTC being greater than cognitive DTC. Conclusion. The interplay of different systems seems to play a crucial role in walking, especially in children with DS. DT walking paradigms with directional changes are recommended for future studies, as this is more appropriate for the everyday demands of children.

Increased prefrontal activity during usual walking in aging

Executive functions are important for successful accomplishment of walking tasks, particularly during a dual task. Over the past few years, several studies investigated prefrontal cortex activity under different walking conditions in older adults with functional near infrared spectroscopy (fNIRS). However, little is known about changes in dorsolateral prefrontal cortex (DLPFC) activity during walking in the early stages of aging. The main objective of this study was to compare changes in DLPFC activity during simple and dual task walking across three different age groups. Twenty-five young (age range = 18–37), twenty-five youngest-old (age range = 55–65), and twenty-five older adults (age range = 67–87) participated in this study. Main results showed that, during simple task walking, older adults had increased DLPFC activity with equivalent walking performance. This increased mainly concerned the right hemisphere. During dual task walking, older adults had increased right DLPFC activity but seemed to have enough resources to maintain their performance during DT walking. This result supports the idea that compensation mechanisms, due to loss of automaticity of walking in aging, appear already during simple task walking. Measuring cortical activity with fNIRS during a simple task walking might be used as valuable indicator for identifying individuals at risk of falling.

Physical Function, An Adjunct to Brain Health Score for Phenotyping Cognitive Function Trajectories in Older Age: Findings From The Irish Longitudinal Study on Ageing (TILDA).

Evidence is limited regarding the cumulative effect of risk factors on cognitive decline and the added value of physical function for cognitive function trajectory stratification. We operationalize 13 modifiable dementia risk factors in a scoring system and investigate the relationship between this brain health score, combined with simple measures of physical function, and risk of cognitive decline. Population-based cohort study of persons aged 50 and older from the Irish Longitudinal Study on Ageing without a history of dementia at baseline who underwent repeated neuropsychological tests (8.08 ± 0.3-year follow-up) were included in the analyses. Exposures were the number of brain health metrics (defined by the Lancet Commission on Dementia Prevention, Intervention, and Care report) at recommended optimal levels. Physical function exposures included Timed Up and Go, dual-task walking speed, and grip strength. Each health metric and physical function measure at the recommended level was assigned a value of 1 and combined to generate brain health scores. Relationship with group-based trajectories of global cognitive function (multidomains composite score), estimated using K-means for longitudinal data, was assessed via ordinal logistic regressions. Among 2 327 participants (mean age, 61 years; 54% women), each additional optimal metric on the brain health score (odds 0.67 [0.62, 0.73]) was associated with reduced odds of cognitive decline. Adding Timed Up and Go (odds 0.71 [0.59, 0.84]) and dual-task walking speed (odds 0.74 [0.63, 0.89]) further improved model fit (ΔAIC = 14.8). These findings support the promotion and maintenance of physical function in addition to brain health strategies to reduce the risk of cognitive decline.

Association between fall risk and assessments of single-task and dual-task walking among community-dwelling individuals with chronic stroke: A prospective cohort study

BackgroundFalling and fall-related injuries are common among community-dwelling individuals with chronic stroke. Falls often occur during dual-task walking scenarios. Accurate fall prediction is critical for formulating effective fall prevention strategies. Research questionsCan dual-task walking tests and corresponding single-task tests predict falls among individuals with chronic stroke? Are dual-task walking tests involving visuospatial cognition more effective in predicting falls than those involving other cognitive domains? MethodsNinety-three individuals with stroke (age: 62.4 ± 6.7 years; stroke duration: 5.6 ± 4.5 years) participated in this prospective cohort study. Two mobility tasks (level-ground walking and obstacle-crossing) were performed with and without two cognitive tasks (auditory clock test and auditory Stroop test). Demographic information and clinical measures of depression, motor function, walking speed and balance were collected. Monthly telephone interviews were conducted to collect data on fall incidence, related circumstances and injuries incurred during a 12-month follow-up period. Multivariate logistic regression analysis was performed to identify predictive factors associated with future risk of falls. ResultsThirty-six participants (39%) reported one or more falls during the follow-up period. The regression model including reaction time during the auditory clock task performance while negotiating obstacles correctly classified the fall status of 80% of the participants (72% future fallers and 84% non-fallers). Performance did not differ between fallers and non-fallers on any other measures tested. SignificanceDual-task assessment combining an auditory clock task with an obstacle-crossing task has potential clinical utility for identifying future fall risk among people with chronic stroke.

Electrocortical Activity in Older Adults Is More Influenced by Cognitive Task Complexity Than Concurrent Walking.

Human cognitive-motor performance largely depends on how brain resources are allocated during simultaneous tasks. Nonetheless, little is known regarding the age-related changes in electrocortical activity when dual-task during walking presents higher complexity levels. Thus, the aim of this study was to investigate whether there are distinct changes in walking performance and electrocortical activation between young and older adults performing simple and complex upper limb response time tasks. Physically active young (23 ± 3 years, n = 21) and older adults (69 ± 5 years, n = 19) were asked to respond as fast as possible to a single stimuli or a double stimuli appearing on a touch screen during standing and walking. Response time, step frequency, step frequency variability and electroencephalographic (EEG) N200 and P300 amplitudes and latencies from frontal central and parietal brain regions were recorded. The results demonstrated that older adults were 23% slower to respond to double stimuli, whereas younger adults were only 12% slower (p < 0.01). The longer response time for older adults was accompanied by greater step frequency variability following double-stimuli presentations (p < 0.01). Older adults presented reduced N200 and P300 amplitudes compared to younger participants across all conditions (p < 0.001), with no effects of posture (standing vs walking) on both groups (p > 0.05). More importantly, the P300 amplitude was significantly reduced for older adults when responding to double stimuli regardless of standing or walking tasks (p < 0.05), with no changes in younger participants. Therefore, physically active older adults can attenuate potential walking deficits experienced during dual-task walking in simple cognitive tasks. However, cognitive tasks involving decision making influence electrocortical activation due to reduced cognitive resources to cope with the task demands.

Impaired Inhibitory Control During Walking in Parkinson's Disease Patients: An EEG Study.

The performance on a visual Go/NoGo (VGNG) task during walking has been used to evaluate the effect of gait on response inhibition in young and older adults; however, no work has yet included Parkinson's disease (PD) patients for whom such changes may be even more enhanced. In this study, we aimed to explore the effect of gait on automatic and cognitive inhibitory control phases in PD patients and the associated changes in neural activity and compared them with young and older adults. 30 PD patients, 30 older adults, and 11 young adults performed a visual Go/NoGo task in a sitting position and during walking on a treadmill while their EEG activity and gait were recorded. Brain electrical activity was evaluated by the amplitude, latency, and scalp distribution of N2 and P300 event related potentials. Mix model analysis was used to examine group and condition effects on task performance and brain activity. The VGNG accuracy rates in PD patients during walking were lower than in young and older adults (F = 5.619, p = 0.006). For all groups, N2 latency during walking was significantly longer than during sitting (p = 0.013). In addition, P300 latency was significantly longer in PD patients (p < 0.001) and older adults (p = 0.032) during walking compared to sitting and during 'NoGo' trials compared with 'Go' trials. Moreover, the young adults showed the smallest number of electrodes for which a significant differential activation between sit to walk was observed, while PD patients showed the largest with N2 being more strongly manifested in bilateral parietal electrodes during walking and in frontocentral electrodes while seated. The results show that response inhibition during walking is impaired in older subjects and PD patients and that increased cognitive load during dual-task walking relates to significant change in scalp electrical activity, mainly in parietal and frontocentral channels.

Neural correlates of dual-task walking in people with central neurological disorders: a systematic review.

People with central neurological disorders experience difficulties with dual-task walking due to disease-related impairments. The objective of this review was to provide a comprehensive examination of the neural correlates (structural/functional brain changes) of dual-task walking in people with Parkinson's disease (PD), multiple sclerosis (MS), stroke, and Alzheimer's disease (AD). A systematic review of the literature was conducted, following PRISMA guidelines, on Medline, Embase, and Scopus. Included studies examined the relationship between structural and functional brain imaging and dual-task walking performance in people with PD, MS, stroke, and AD. Articles that met the inclusion criteria had baseline characteristics, study design, and behavioral and brain outcomes extracted. Twenty-three studies were included in this review. Most structural imaging studies (75%) found an association between decreased brain integrity and poor dual-task performance. Specific brain regions that showed this association include the striatum regions and hippocampus in PD and supplementary motor area in MS. Functional imaging studies reported an association between increased prefrontal activity and maintained (compensatory recruitment) or decreased dual-task walking performance in PD and stroke. A subset (n = 2) of the stroke papers found no significant correlations. Increased supplementary motor area activity was associated with decreased performance in MS and stroke. No studies on AD were identified. In people with PD, MS, and stroke, several neural correlates of dual-task walking have been identified, however, the direction of the association between neural and performance outcomes varied across the studies. The type of cognitive task used and presentation modality (e.g., visual) may have contributed to these mixed findings.

Effect of early integrated robot-assisted gait training on motor and balance in patients with acute ischemic stroke: a single-blinded randomized controlled trial.

Background:Gait disruption is a common poststroke problem. Robot-assisted gait training (RAGT) might improve motor function, balance, and activities of daily living.Objective:We compared the clinical effectiveness of early integrated RAGT using the Walkbot robotic gym with an intensity-matched enhanced lower limb therapy (ELLT) program and with conventional rehabilitation therapy (CRT) in patients with acute ischemic stroke.Methods:A total of 192 patients with acute ischemic stroke were randomly assigned (1:1:1) to receive RAGT, ELLT, or CRT. All three groups received 45 min of training daily, 3 days a week, for 4 weeks consecutively. Before and after the 4-week treatment, the patients were assessed based on a 6-minute walking test (6MWT), functional ambulation classification (FAC), timed up and go (TUG) test, dual-task walking (DTW) test, Tinetti’s test, Barthel’s index (BI), stroke-specific quality of life (SS-QOL) scale, and gait analysis parameters.Results:After the 4-week intervention, the results of the 6MWT, FAC, TUG, DTW, Tinetti’s test, BI, SS-QOL, and gait in the three groups significantly improved. Compared with ELLT and CRT groups, participants in the RAGT group had a better performance in 6MWT (199.11 ± 60.72 versus 182.47 ± 59.72 versus 173.69 ± 40.58, p = 0.035), FAC (4.10 ± 0.91 versus 3.69 ± 0.88 versus 3.58 ± 0.81, p = 0.044), DTW (10.29 ± 2.38 versus 12.92 ± 2.64 versus 13.89 ± 2.62, p = 0.031), SS-QOL (184.46 ± 20.53 versus 165.39 ± 20.49 versus 150.72 ± 20.59, p = 0.012), velocity (0.66 ± 0.22 versus 0.55 ± 0.23 versus 0.51 ± 0.20, p = 0.008), cycle duration (1.38 ± 0.40 versus 1.50 ± 0.38 versus 1.61 ± 0.30, p = 0.040), and swing phase symmetry ratio (SPSR, 1.10 ± 0.33 versus 1.21 ± 0.22 versus 1.48 ± 0.25, p = 0.021). The TUG, Tinetti’s test, BI, and RMT results were similar, however.Conclusion:In the acute stroke phase, early integrated RAGT showed greater performance in gait rehabilitation than CRT and ELLT.Registration:ChiCTR1900026225

Spatio-temporal gait differences in Facioscapulohumeral muscular dystrophy during single and dual task overground walking - A pilot study

Facioscapulohumeral muscular dystrophy (FSHD) is a rare genetic muscle disorder leading to progressive muscle loss over time. Research indicates that this progressive muscular atrophy can negatively impact spatio-temporal gait characteristics, but this is not always the case during early-onset or mild cases of the disease. In addition, the performance of a secondary task during overground walking may elucidate greater deficits in spatio-temporal characteristics of gait. However, such dual task effects on FSHD gait have not been studied thus far. The current study aimed to (a) quantify changes in spatio-temporal gait parameters in individuals with FSHD using the Tekscan Strideway gait mat system, (b) measure the dual task (DT) effects on cadence and gait velocity during single task (ST) and DT overground walking in FSHD and healthy controls and (c) investigate the correlation between the gait parameters and the methylation status in FSHD. Nine FSHD (M±SD=52.78±14.69 years) and nine nearly matched healthy controls (M±SD=50.11±16.18 years) performed five ST and five DT walking in a pseudo-randomized order. The DT included a serial 7's subtraction task from a random number between 50 and 100. Dependent variables: Cadence (steps/min) and gait velocity (cm/sec) were obtained from Tekscan Strideway (30 Hz, Boston, MA). The pairwise comparison indicated that cadence was significantly different for both ST (P<0.004) and DT (P<0.02) where FSHD showed lower cadence compared to controls. Gait velocity was also significantly lower for FSHD during ST (P<0.004) and DT (P<0.008). Multilevel modeling (MLM) approach revealed a group by task interaction for cadence (P<0.05) and gait velocity (P<0.001). The interaction showed a significant difference between ST and DT in controls for cadence and gait velocity. However, there was no difference between ST and DT in FSHD. Finally, a comparison of methylation percentage versus gait parameters revealed a significant negative correlation coefficient for cadence but not for gait velocity. These results indicate specific pairwise differences in both ST and DT walking, observed in the gait parameters as decreased cadence and gait velocity during ST and DT. In addition, the MLM showed that controls exhibited the DT cost as expected but FSHD did not for cadence and gait velocity. ST appears to be sufficiently challenging in FSHD and results in overall declines in spatio-temporal characteristics of gait. Further research is needed to test this paradigm with early-onset or mild cases to track disease progression and its effects on ambulation.

Automated Prescreening of Mild Cognitive Impairment Using Shank-Mounted Inertial Sensors Based Gait Biomarkers

The mild symptoms in Mild Cognitive Impairment (MCI), a precursor of dementia, often go unnoticed and are assumed as normal aging signs. Such negligence result in late visits which consequently, lead to the diagnosis and progression of dementia. An instrumented gait assessment in home settings may facilitate the detection of subtle MCI-related motor deficits thus, allowing early diagnosis and intervention. This paper investigates potential gait biomarkers derived from shank mounted inertial sensors signals under normal and dual-task walking conditions using data collected from thirty MCI and thirty cognitively normal (CN) subjects. To identify potential gait biomarkers for MCI screening, we assess the variance and predictive power of each feature. Moreover, multiple classification models using different machine learning and feature selection techniques are built to automate MCI detection by leveraging the gait biomarkers. Statistical analysis reveal multiple gait parameters that are significantly different under both single and dual-task settings. However, we show that dual-task walking provides better distinction between MCI and CN subjects. The machine learning model employed for MCI pre-screening based on the inertial sensor-derived gait biomarkers achieves accuracy and sensitivity of 71.67% and 83.33%, respectively.

The effect of a multi-modal boxing exercise program on cognitive locomotor tasks and gait in persons with Parkinson disease.

Parkinson disease (PD) is a progressive neurological disease resulting in motor impairments, postural instability, and gait alterations which may result in self-care limitations and loss of mobility reducing quality of life. This study's purpose was to determine the impact of a community-based boxing program on gait parameters, dual task and backwards walking in individuals with PD. This study included 26 community dwelling individuals with PD who participated in 12-week boxing classes (1 hour, 2 times a week). The focus was on upper/lower extremity exercises using punching bags, agility drills, and strengthening activities. Pre/post testing was performed for dual task and gait parameters and was analyzed using t-tests. Analysis of the scores indicated participants performed significantly better at post-test compared to pre-test on self-selected walking velocity (P = 0.041), cadence (P = 0.021); backwards walking velocity (P = 0.003), step length (P = 0.022); dual task walking velocity (P = 0.044), step length (P = 0.023), and gait variability index (P = 0.008). No significant differences for fast walking. Multi-modal boxing produced improvements in gait velocity, dual task velocity, step length, and gait variability, as well as backwards walking velocity and step length. These improvements may impact independence with functional mobility and may improve safety but require further studies.

Dual task walking in healthy aging: Effects of narrow and wide walking paths.

Dual-task walking may lead to gait instability and a higher fall risk in older adults, particularly when walking in a busy city street. Challenging street features such as narrow sidewalks not only discourage walking, but are also likely to be taxing for older adults’ cognitive resources and gait characteristics. The aim of this study was to assess the way older adults’ gait characteristics are affected by walking on a narrow path while performing a challenging cognitive task in lab conditions imitating common urban environments. Nineteen young and eighteen older adults walked on a narrow (40cm) and a wide (80cm) path and performed a cognitive (n-back) task individually adjusted to 80% accuracy. The two tasks were performed separately (Single-Task) and concurrently (Dual-Task). Both groups walked faster, and their step width was narrower on the narrow path. During dual-task walking on the narrow path, older adults showed significant dual-task costs in the cognitive task, gait speed, step width, and stride length. Dual-task walking was associated with decreased gait speed and stride length in both age groups, suggesting that dual-task walking may adversely affect gait, particularly when walking on narrow paths. These conditions may lead to gait instability and an increased fall risk for older adults, particularly when walking along the narrow sidewalks commonly found within the built environment. However, more research is needed in an urban setting to determine the extent of the fall risk narrow sidewalks present for older adults.

Effect of Heart Rate Reserve on Prefrontal Cortical Activation While Dual-Task Walking in Older Adults.

Hypertension is considered a risk factor for cardiovascular health and non-amnestic cognitive impairment in older adults. While heart rate reserve (HRR) has been shown to be a risk factor for hypertension, how impaired HRR in older adults can lead to cognitive impairment is still unclear. The objective of this study was to examine the effects of HRR on prefrontal cortical (PFC) activation under varying dual-task demands in older adults. Twenty-eight older adults (50–82 years of age) were included in this study and divided into higher (n = 14) and lower (n = 14) HRR groups. Participants engaged in the cognitive task which was the Modified Stroop Color Word Test (MSCWT) on a self-paced treadmill while walking. Participants with higher HRR demonstrated increased PFC activation in comparison to lower HRR, even after controlling for covariates in analysis. Furthermore, as cognitive task difficulty increased (from neutral to congruent to incongruent to switching), PFC activation increased. In addition, there was a significant interaction between tasks and HRR group, with older adults with higher HRR demonstrating increases in PFC activation, faster gait speed, and increased accuracy, relative to those with lower HRR, when going from neutral to switching tasks. These results provide evidence of a relationship between HRR and prefrontal cortical activation and cognitive and physical performance, suggesting that HRR may serve as a biomarker for cognitive health of an older adult with or without cardiovascular risk.

Motor Skill Training Effect on Real-Time Prefrontal Cortex Activation During Walking

We aimed to test the effects of motor skill training (MST) on gait automaticity measured by changes in prefrontal cortex (PFC) activation during actual walking. We used data from a 12-week trial of older adults (mean age=75.5, 60.5% women) randomized to standard physical therapy and standard+MST in a 1:1 ratio. Functional near infrared spectroscopy (fNIRS) measured PFC activation during simple and dual task walking. We will apply linear mixed models to assess effects of task, time, and MST on PFC activation. We will compare the PFC activation 1) during dual task walking compared to simple walking; 2) across visits after intervention; and 3) between participants receiving MST compared to standard physical therapy. These results will demonstrate whether gait automaticity, as evidenced by PFC activation during walking, is affected by MST.

Effects of Age on Dual Task Walking Performance as Measured Using a Smartphone Application in Middle-Aged Adults

After the age of 65, one’s ability to walk while performing an additional cognitive task (i.e., dual-tasking) is predictive of both future falls and cognitive decline. However, while it is well-known that older adults exhibit diminished dual-task performance, the time course of age-related dual-task decline has not been established. We thus conducted an analysis of data collected within the ongoing Barcelona Brain Health Initiative, a prospective population-based study characterizing the determinants of brain health maintenance in middle-aged adults. Cognitively-unimpaired participants (n=655) aged 40-65 years without neuro-psychiatric disease completed laboratory-based trials of walking normally (single-task) and walking while performing a verbalized serial subtraction task (dual-task). A smartphone-based gait assessment application was used to capture data and derive both the mean stride time (ST) and stride time variability (STV, defined as the coefficient of variation about the mean stride time) of each trial. The dual-task costs (DTC) to each gait metric were obtained by calculating the percent change from single- to dual-task conditions. We categorized participants into five groups according to age (e.g. Group 1: 40-45 years; Group 5: 60-65 years). Age group did not have an effect on single-task gait outcomes (p>0.51). However, the oldest age group, as compared to each of the other groups, exhibited greater DTC to both ST and STV (p<0.03). These results indicate that dual-task walking performance in particular may begin to diminish in late middle age even in the absence of detectable cognitive issues, DTC may offer a sensitive metric to age-related change in cognitive function.

An intensive exercise-based training program reduces prefrontal activity during usual walking in patients with Parkinson’s disease

IntroductionParkinson’s disease (PD) leads to a progressive loss of locomotor automaticity. Consequently, PD patients rely more on executive resources for the control of gait, resulting in increased prefrontal activity while walking. Exercise-based training programs may improve automaticity of walking and reduce prefrontal activity in this population. This study aimed to assess the effect of an intensive multidisciplinary exercise-based training program on prefrontal activity and gait performance during usual walking in PD patients. MethodFourteen patients (mean age: 67 ± 9; disease duration: 6 ± 5 years; Hoehn and Yahr score: 1.9 ± 0.6) were included in this study. They were assessed in ON stage at three different times at 5-week intervals: two times before the training program (T0 and T1) and once after the training program (T2). Gait performance (stride time, speed, stride length, cadence, and their respective coefficient of variation) and cortical activity in the dorsolateral prefrontal cortex (DLPFC) using functional near infrared spectroscopy (fNIRS) were measured during usual walking. ResultsPatients had reduced cortical activity of the DLPFC at T2 compared to T1 (p = 0.003). Patients had shorter stride time at T2 compared to T1 (p = 0.025) and tended to have longer stride length at T2 than at T1 (p = 0.056). ConclusionThe training program led to positive effects on prefrontal activity and gait performance. Reduced prefrontal activity during usual walking after training program suggests that patients may have a greater reserve capacity to face more challenging walking conditions. Further studies will investigate the effect of this training on cortical activity during dual-task walking..

Combining Transcranial Direct Current Stimulation With Tai Chi to Improve Dual-Task Gait Performance in Older Adults With Mild Cognitive Impairment: A Randomized Controlled Trial.

Introduction: Engaging in a secondary task while walking increases motor-cognitive interference and exacerbates fall risk in older adults with mild cognitive impairment (MCI). Previous studies have demonstrated that Tai Chi (TC) may improve cognitive function and dual-task gait performance. Intriguingly, with emerging studies also indicating the potential of transcranial direct current stimulation (tDCS) in enhancing such motor-cognitive performance, whether combining tDCS with TC might be superior to TC alone is still unclear. The purpose of this study was to investigate the effects of combining tDCS with TC on dual-task gait in patients with MCI.Materials and Methods: Twenty patients with MCI were randomly assigned to receive either anodal or sham tDCS, both combined with TC, for 36 sessions over 12 weeks. Subjects received 40 min of TC training in each session. During the first 20 min, they simultaneously received either anodal or sham tDCS over the left dorsolateral prefrontal cortex. Outcome measures included dual-task gait performance and other cognitive functions.Results: There were significant interaction effects between groups on the cognitive dual task walking. Compared to sham, the anodal tDCS group demonstrated a greater improvement on cadence and dual task cost of speed.Conclusion: Combining tDCS with TC may offer additional benefits over TC alone in enhancing dual-task gait performance in patients with MCI.Clinical Trial Registration: [www.ClinicalTrials.gov], identifier [TCTR20201201007].

Walking While Talking and Prefrontal Oxygenation in Motoric Cognitive Risk Syndrome: Clinical and Pathophysiological Aspects.

Motoric cognitive risk syndrome (MCR) combines slow gait and cognitive complaints and has been proposed as a predementia syndrome. The nature of dual-task performance in MCR has not been established. To assess differences in dual-task performance between participants with and without MCR and to study the prefrontal cortex (PFC)-based brain activity during dual-task using functional near-infrared spectroscopy. Cohort study of community-dwelling non-demented older adults included in the "Central Control of Mobility in Aging" study. Comprehensive assessment included global cognition and executive function tests along with clinical variables. Dual-task paradigm consisted in walking while reciting alternate letters of the alphabet (WWT) on an electronic walkway. We compared dual-task performance between MCR (n = 60) and No MCR (n = 478) participants and assessed the relationship of dual-task performance with cognitive function. In a subsample, we compared PFC oxygenation during WWT between MCR (n = 32) and No MCR (n = 293). In our sample of 538 high-functioning older adults (76.6±6.5 years), with 11.2% prevalence of MCR, dual-task cost was not significantly different, compared to No MCR participants. Among MCR participants, no significant relationship was found between WWT velocity and cognitive function, whereas No MCR participants with better cognitive function showed faster WWT velocities. PFC oxygenation during WWT was higher in MCR compared to No MCR (1.02±1.25 versus 0.66±0.83, p = 0.03). MCR participants showed no significant differences in the dual-task cost while exhibiting higher PFC oxygenation during dual-task walking. The dual-task performance (WWT velocity) in MCR participants was not related to cognition.

Bi-Anodal Transcranial Direct Current Stimulation Combined With Treadmill Walking Decreases Motor Cortical Activity in Young and Older Adults

Background: Walking in the “real world” involves motor and cognitive processes. In relation to this, declines in both motor function and cognition contribute to age-related gait dysfunction. Transcranial direct current stimulation (tDCS) and treadmill walking (STW) have potential to improve gait, particularly during dual-task walking (DTW); walking whilst performing a cognitive task. Our aims were to analyze effects of combined anodal tDCS + STW intervention on cortical activity and gait during DTW.Methods: Twenty-three young adults (YA) and 21 older adults (OA) were randomly allocated to active or sham tDCS stimulation groups. Participants performed 5-min of mixed treadmill walking (alternating 30 s bouts of STW and DTW) before and after a 20-min intervention of active or sham tDCS + STW. Anodal electrodes were placed over the left prefrontal cortex (PFC) and the vertex (Cz) using 9 cm2 electrodes at 0.6 mA. Cortical activity of the PFC, primary motor cortex (M1), premotor cortex (PMC), and supplementary motor area (SMA) bilaterally were recorded using a functional near-infrared spectroscopy (fNIRS) system. Oxygenated hemoglobin (HbO2) levels were analyzed as indicators of cortical activity. An accelerometer measured gait parameters. We calculated the difference between DTW and STW for HbO2 and gait parameters. We applied linear mixed effects models which included age group (YA vs. OA), stimulation condition (sham vs. active), and time (pre- vs. post-intervention) as fixed effects. Treadmill belt speed was a covariate. Partial correlation tests were also performed.Results: A main effect of age group was observed. OA displayed higher activity bilaterally in the PFC and M1, unilaterally in the right PMC and higher gait variability than YA. M1 activity decreased in both YA and OA following active tDCS + STW. There was no overall effect of tDCS + STW on PFC activity or gait parameters. However, negative correlations were observed between changes in left PFC and stride length variability following active tDCS + STW intervention.Conclusion: Increased activity in multiple cortical areas during DTW in OA may act as a compensatory mechanism. Reduction in M1 activity following active tDCS + STW with no observed gait changes suggests improved neural efficiency.

Cognition differentiates gait speed among older adults

AbstractBackgroundThe ability to perform a motor and cognitive dual‐task (DT) becomes more challenging as one ages and shows a greater deficit, if one has a cognitive impairment (CI). CI has also been shown to predict a decline in physical functioning. Therefore, the purpose was to examine differences between cognitively healthy (CN) and cognitively impaired (CI) older adults on gait speed (GS) during habitual (HAB) and fast (FAST) walking trials with and without a DT.Method83 older adults (80.66±5.36) completed a digital Visual Paired Comparison (VPC) cognitive assessment, which measured working memory, and a Digital Symbol (DS) cognitive assessment, which measured processing speed. Participants were grouped into CN or CI based on their results for each assessment. Subjects performed two trials of each walking test: HAB, FAST, HAB‐DT, and FAST‐DT. The DT trials were performed using a working memory task. GS was calculated using the time to cover 10m. One‐way ANOVA was used to assess for differences in GS between VPC and DS cognitive groups.ResultWhile HAB GS (p=.10) was not significantly different between the VPC cognitive groups, the CN group walked significantly faster than the CI group during the FAST, HAB DT, and FAST DT trials (p&lt;.05). There was not a significant difference in HAB GS (p=.10) or HAB DT GS (p=.08) between the CI and CN DS groups. However, the DS CI group walked significantly slower during the FAST (p=.03) and FAST DT (p=.05) assessments.ConclusionIndividuals with CI showed no statistical difference in habitual walking speed. However, this was clinically meaningful as the individuals with an average or above average working memory and processing speed walked faster than individuals with CI by 8.4% and 6.5%, respectively. While GS declined during the DT trials, individuals with a working memory impairment showed a greater decline, and it was even larger during the fast DT trials and for individuals with a working memory (19.5%) or processing speed (17.6%) impairment. Previous research has suggested DT walking involves activation of the prefrontal cortex, which may partially explain the greater decline in DT GS for those with working memory impairment.